How do I input an array whose length may vary? The input is space delimited and ends when I press enter
public class ArrayInput {
public static void main(String args[]){
ArrayList<Integer> al = new ArrayList<Integer>();
Scanner sc = new Scanner(System.in);
while(){//what condition to use here?
al.add(sc.nextInt());
}
}
}
An example would be:
1 2 5 9 7 4 //press enter here to mark end of input
Since all your input is in a single line, you can read the entire line and then split it to integers :
String line = sc.nextLine();
String[] tokens = line.split(" ");
int[] numbers = new int[tokens.length];
for (int i=0; i<numbers.length;i++)
numbers[i] = Integer.parseInt(tokens[i]);
Read the entire line using sc.nextLine() and then split() using \\s+. This way, you don't have to worry about size of input (number of elements). Use Integer.parseInt() to parse Strings as integers.
I'm attempting to take an input from the user, then if it matches one of the existing files, read the file and put the words, letters, or number into an array. The "words", and "alphabet" files seem to work fine, but the "numbers" is giving me an issue. It finds the file, reads it, puts it into an array, and gives the summation of the numbers; however, the output of the array is every other number, as opposed to all numbers, like it should be doing.
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
public class fileIO
{
public static void main (String[] args) throws FileNotFoundException
{
String filename;
System.out.println("Please enter name of file (alphabet,words,numbers): ");
Scanner input = new Scanner(System.in);
filename = input.nextLine();
if(filename.equals("numbers"))
{
int sum = 0;
Scanner reader = new Scanner(new File("/home/ninjew/workspace/FileIO/src/" + filename + ".txt"));
ArrayList<Integer> arr = new ArrayList<Integer>();
while(reader.hasNext())
{
arr.add(reader.nextInt());
sum = sum + reader.nextInt();
}
System.out.println(arr);
System.out.println("The summation is: " + sum);
reader.close();
}
else if(filename.equals("words") || filename.equals("alphabet"))
{
Scanner reader = new Scanner(new File("/home/ninjew/workspace/FileIO/src/" + filename + ".txt"));
// This is for words and letters within the file. Print words and letters.
ArrayList<String> arr = new ArrayList<String>();
while(reader.hasNext())
{
String line = reader.next();
Scanner scanner = new Scanner(line);
scanner.useDelimiter(",");
while(scanner.hasNext()){
arr.add(scanner.next());
}
scanner.close();
}
System.out.println(arr);
reader.close();
}
}
}
In if(filename.equals("numbers")) you are doing two reads from your file in this block, which is why it is skipping numbers
while(reader.hasNext())
{
arr.add(reader.nextInt());
sum = sum + reader.nextInt();
}
Should be
while(reader.hasNext())
{
int val = reader.nextInt();
arr.add(val);
sum = sum + val;
}
Your numbers reader loop is adding first number to the array and the next number to the sum.
If input is 1 2 3 4 5 6, your array is [1, 3, 5] and your sum is 2 + 4 + 6 = 12.
You are reading next two integers in one go. Every time you call scanner.nextInt() it will read a next int. You need to store nextInt in a temp variable and use it in both the places.
while(reader.hasNext())
{
int next = reader.nextInt();
arr.add(next);
sum = sum + next;
}
in one line from the standard input I have 3 types of integers: the first integer is id, the second integer is N - some number, and after that follows N integers, separeted by a single space which I want to store in array or ArrayList. How can I do this using BufferedReader? I have the following code:
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String[] line = br.readLine().split(" ");
int ID = Integer.parseInt(line[0]);
int N = Integer.parseInt(line[1]);
My question is is there any elegant way to read the rest of the line and to store it into array?
Use Scanner and method hasNextInt()
Scanner scanner = new Scanner(System.in);
while (scanner.hasNext()) {
if (scanner.hasNextInt()) {
arr[i]=scanner.nextInt();
i++;
}
}
How can I do this using BufferedReader?
You've already read/split the line, so you can just loop over the rest of the inputted integers and add them to an array:
int[] array = new int[N]; // rest of the input
assert line.length + 2 == N; // or some other equivalent check
for (int i = 0; i < N; i++)
array[i] = Integer.parseInt(line[i + 2]);
This will also let you handle errors within the loop (I'll leave that part to you, should you find it necessary).
I am working on a program and I want to allow a user to enter multiple integers when prompted. I have tried to use a scanner but I found that it only stores the first integer entered by the user. For example:
Enter multiple integers: 1 3 5
The scanner will only get the first integer 1. Is it possible to get all 3 different integers from one line and be able to use them later? These integers are the positions of data in a linked list I need to manipulate based on the users input. I cannot post my source code, but I wanted to know if this is possible.
I use it all the time on hackerrank/leetcode
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String lines = br.readLine();
String[] strs = lines.trim().split("\\s+");
for (int i = 0; i < strs.length; i++) {
a[i] = Integer.parseInt(strs[i]);
}
Try this
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (in.hasNext()) {
if (in.hasNextInt())
System.out.println(in.nextInt());
else
in.next();
}
}
By default, Scanner uses the delimiter pattern "\p{javaWhitespace}+" which matches at least one white space as delimiter. you don't have to do anything special.
If you want to match either whitespace(1 or more) or a comma, replace the Scanner invocation with this
Scanner in = new Scanner(System.in).useDelimiter("[,\\s+]");
You want to take the numbers in as a String and then use String.split(" ") to get the 3 numbers.
String input = scanner.nextLine(); // get the entire line after the prompt
String[] numbers = input.split(" "); // split by spaces
Each index of the array will hold a String representation of the numbers which can be made to be ints by Integer.parseInt()
Scanner has a method called hasNext():
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext())
{
System.out.println(scanner.nextInt());
}
If you know how much integers you will get, then you can use nextInt() method
For example
Scanner sc = new Scanner(System.in);
int[] integers = new int[3];
for(int i = 0; i < 3; i++)
{
integers[i] = sc.nextInt();
}
Java 8
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
int arr[] = Arrays.stream(in.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
Here is how you would use the Scanner to process as many integers as the user would like to input and put all values into an array. However, you should only use this if you do not know how many integers the user will input. If you do know, you should simply use Scanner.nextInt() the number of times you would like to get an integer.
import java.util.Scanner; // imports class so we can use Scanner object
public class Test
{
public static void main( String[] args )
{
Scanner keyboard = new Scanner( System.in );
System.out.print("Enter numbers: ");
// This inputs the numbers and stores as one whole string value
// (e.g. if user entered 1 2 3, input = "1 2 3").
String input = keyboard.nextLine();
// This splits up the string every at every space and stores these
// values in an array called numbersStr. (e.g. if the input variable is
// "1 2 3", numbersStr would be {"1", "2", "3"} )
String[] numbersStr = input.split(" ");
// This makes an int[] array the same length as our string array
// called numbers. This is how we will store each number as an integer
// instead of a string when we have the values.
int[] numbers = new int[ numbersStr.length ];
// Starts a for loop which iterates through the whole array of the
// numbers as strings.
for ( int i = 0; i < numbersStr.length; i++ )
{
// Turns every value in the numbersStr array into an integer
// and puts it into the numbers array.
numbers[i] = Integer.parseInt( numbersStr[i] );
// OPTIONAL: Prints out each value in the numbers array.
System.out.print( numbers[i] + ", " );
}
System.out.println();
}
}
There is more than one way to do that but simple one is using String.split(" ")
this is a method of String class that separate words by a spacial character(s) like " " (space)
All we need to do is save this word in an Array of Strings.
Warning : you have to use scan.nextLine(); other ways its not going to work(Do not use scan.next();
String user_input = scan.nextLine();
String[] stringsArray = user_input.split(" ");
now we need to convert these strings to Integers. create a for loop and convert every single index of stringArray :
for (int i = 0; i < stringsArray.length; i++) {
int x = Integer.parseInt(stringsArray[i]);
// Do what you want to do with these int value here
}
Best way is converting the whole stringArray to an intArray :
int[] intArray = new int[stringsArray.length];
for (int i = 0; i < stringsArray.length; i++) {
intArray[i] = Integer.parseInt(stringsArray[i]);
}
now do any proses you want like print or sum or... on intArray
The whole code will be like this :
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String user_input = scan.nextLine();
String[] stringsArray = user_input.split(" ");
int[] intArray = new int[stringsArray.length];
for (int i = 0; i < stringsArray.length; i++) {
intArray[i] = Integer.parseInt(stringsArray[i]);
}
}
}
This works fine ....
int a = nextInt();
int b = nextInt();
int c = nextInt();
Or you can read them in a loop
Using this on many coding sites:
CASE 1: WHEN NUMBER OF INTEGERS IN EACH LINE IS GIVEN
Suppose you are given 3 test cases with each line of 4 integer inputs separated by spaces 1 2 3 4, 5 6 7 8 , 1 1 2 2
int t=3,i;
int a[]=new int[4];
Scanner scanner = new Scanner(System.in);
while(t>0)
{
for(i=0; i<4; i++){
a[i]=scanner.nextInt();
System.out.println(a[i]);
}
//USE THIS ARRAY A[] OF 4 Separated Integers Values for solving your problem
t--;
}
CASE 2: WHEN NUMBER OF INTEGERS in each line is NOT GIVEN
Scanner scanner = new Scanner(System.in);
String lines=scanner.nextLine();
String[] strs = lines.trim().split("\\s+");
Note that you need to trim() first: trim().split("\\s+") - otherwise, e.g. splitting a b c will emit two empty strings first
int n=strs.length; //Calculating length gives number of integers
int a[]=new int[n];
for (int i=0; i<n; i++)
{
a[i] = Integer.parseInt(strs[i]); //Converting String_Integer to Integer
System.out.println(a[i]);
}
created this code specially for the Hacker earth exam
Scanner values = new Scanner(System.in); //initialize scanner
int[] arr = new int[6]; //initialize array
for (int i = 0; i < arr.length; i++) {
arr[i] = (values.hasNext() == true ? values.nextInt():null);
// it will read the next input value
}
/* user enter = 1 2 3 4 5
arr[1]= 1
arr[2]= 2
and soo on
*/
It's working with this code:
Scanner input = new Scanner(System.in);
System.out.println("Enter Name : ");
String name = input.next().toString();
System.out.println("Enter Phone # : ");
String phone = input.next().toString();
A simple solution can be to consider the input as an array.
Scanner sc = new Scanner(System.in);
int n = sc.nextInt(); //declare number of integers you will take as input
int[] arr = new int[n]; //declare array
for(int i=0; i<arr.length; i++){
arr[i] = sc.nextInt(); //take values
}
You're probably looking for String.split(String regex). Use " " for your regex. This will give you an array of strings that you can parse individually into ints.
Better get the whole line as a string and then use StringTokenizer to get the numbers (using space as delimiter ) and then parse them as integers . This will work for n number of integers in a line .
Scanner sc = new Scanner(System.in);
List<Integer> l = new LinkedList<>(); // use linkedlist to save order of insertion
StringTokenizer st = new StringTokenizer(sc.nextLine(), " "); // whitespace is the delimiter to create tokens
while(st.hasMoreTokens()) // iterate until no more tokens
{
l.add(Integer.parseInt(st.nextToken())); // parse each token to integer and add to linkedlist
}
Using BufferedReader -
StringTokenizer st = new StringTokenizer(buf.readLine());
while(st.hasMoreTokens())
{
arr[i++] = Integer.parseInt(st.nextToken());
}
When we want to take Integer as inputs
For just 3 inputs as in your case:
import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int a,b,c;
a = scan.nextInt();
b = scan.nextInt();
c = scan.nextInt();
For more number of inputs we can use a loop:
import java.util.Scanner;
Scanner scan = new Scanner(System.in);
int a[] = new int[n]; //where n is the number of inputs
for(int i=0;i<n;i++){
a[i] = scan.nextInt();
}
This method only requires users to enter the "return" key once after they have finished entering numbers:
It also skips special characters so that the final array will only contains integers
ArrayList<Integer> nums = new ArrayList<>();
// User input
Scanner sc = new Scanner(System.in);
String n = sc.nextLine();
if (!n.isEmpty()) {
String[] str = n.split(" ");
for (String s : str) {
try {
nums.add(Integer.valueOf(s));
} catch (NumberFormatException e) {
System.out.println(s + " cannot be converted to Integer, skipping...");
}
}
}
//Get user input as a 1 2 3 4 5 6 .... and then some of the even or odd number like as 2+4 = 6 for even number
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int evenSum = 0;
int oddSum = 0;
while (n > 0) {
int last = n % 10;
if (last % 2 == 0) {
evenSum += last;
} else {
oddSum += last;
}
n = n / 10;
}
System.out.println(evenSum + " " + oddSum);
}
}
if ur getting nzec error, try this:
try{
//your code
}
catch(Exception e){
return;
}
i know it's old discuss :) i tested below code it's worked
`String day = "";
day = sc.next();
days[i] = Integer.parseInt(day);`
I need to solve the following problem: Write a method named tokenStats that accepts as a parameter a Scanner containing a series of tokens. It should print out the sum of all the tokens that are legal integers, the sum of all the tokens that are legal real numbers but not integers, and the total number of tokens of any kind. For example, if a Scanner called data contains the following tokens:
3 3.14 10 squid 10.x 6.0
Then the call of tokenStats(data); should print the following output:
integers: 13
real numbers: 9.14
total tokens: 6
If the Scanner has no tokens, the method should print:
integers: 0
real numbers: 0.0
total tokens: 0
So, this is my question. I have tried to use
while (input.hasNext()) {
if (input.hasNextInt()) {
and this creates an infinite loop,
but if I use
while (input.hasNext()) {
input.next();
if (input.hasNextInt()) {
I lose my first token if it is an int...
what should I do?
I suggest you check this way .. which cover all your scenario
int totalint =0;
float totalfloat=0 ;
int count=0;
while(input.hasNext())
{
String next = input.next();
int n; float f;
try{
if(next.contains(".")
{
f= Float.parseFloat(next);
totalfloat += f;
}
else{
n= Integer.parseInt(next);
totalint +=n;
}
}
catch(Exception e){ /*not int nor a float so nothing*/ }
count++;
}
In order to determine the amount of Integers in your file I suggest doing something like this
Add the following variables to your code
ArrayList<Integer> list = new ArrayList<Integer>();
int EntryCount = 0;
int IntegerCount =0;
Then when looking through the file inputs try something like this were s is an instance of a scanner
while (s.hasNext()) {
if(s.hasNextInt() == true){
int add =s.nextInt();
System.out.println(add);
list.add(add);
IntegerCount++;
}
EntryCount++;
}
Then in order to figure out the sum of all integers you would loop through the array list.
public static void tokenStats(Scanner input) {
int integers = 0;
double real = 0.0;
int tokens = 0;
while (input.hasNext()) {
if (input.hasNextInt()) {
integers+= input.nextInt();
} else if (input.hasNextDouble()) {
real+= input.nextDouble();
} else {
input.next();
}
tokens++;
}
System.out.println("integers: " + integers);
System.out.println("real numbers: " + real);
System.out.println("total tokens: " + tokens);
}